variance

A student wants to calculate the variance of a set of 10 scores. Unfortunately, he doesn't have the raw scores but only has the deviation of each raw score from the mean. Worse yet, he only has 9 of these deviation scores, as listed below. Compute the variance for him.

A student wants to calculate the variance of a set of 10 scores. Unfortunately, he doesn't have the raw scores but only has the deviation of each raw score from the mean. Worse yet, he only has 9 of these deviation scores, as listed below. Compute the variance for him.

-5, +11, -4, -2, +7, -8, -6, +1, -3

I have no idea how to do this problem

The last deviation can be found as the mean of the deviations from the mean
is zeros. So let be the missing deviation, then: